This is an underwater phenomenon in arctic areas.
When sea ice forms it can leave behind brine that is so cold yet salty, it falls down through the sea water - causing that to freeze into a tube and form a "Brinacle". - an icicle formed of brine.https://www.youtube.com/watch?v=lAupJzH31tc

This intense cold is brought from the surface to the depths, and will kill any creature it entraps in ice.

On reaching the seafloor, it will continue to accumulate ice as surrounding water freezes. The brine will travel along the seafloor in a down-slope direction until it reaches the lowest possible point, where it will pool. Any bottom-dwelling sea creatures, including starfish or sea urchins can be encased in this expanding web of ice and be trapped, ultimately freezing to death.